Polyelectrolyte Thin Films As a Platform for pH-Responsive Lipid Membranes

We present a robust and simple method for the preparation of pH-responsive lipid membranes. Polymeric cushions to support a lipid bilayer were obtained by performing layer-by-layer  (LbL) deposition of a polycation and a polyanion on quartz, with polycation as a capping layer.  A model lipidic membrane was obtained by depositing 1,2-Dipalmitoyl-sn-glycero-3-phophoethanolamine (DPPE) bilayer using Langmuir-Blodgett and Langmuir-Schäfer technique. Neutron Reflectivity experiments revealed that the separation distance between the polymeric cushion and the DPPE bilayer can be reversibly adjusted by varying the pH of the aqueous environment. We believe that electrostatic interactions between the polymeric cushion and the DPPE bilayer play an important role in affecting the separation distance between the same.  Similar pH-dependent lift-off was also observed with DPPC bilayer deposited on similar polymeric cushions. It is noteworthy that this pH-dependent behavior was found to be reversible. We believe that this novel system offers great potential for fundamental biophysical studies of membrane properties decoupled from the underlying solid support.